The use of aromatic amines as stabilizers for lubricant compositions is well-known in the art. U.S. Pat. Nos. 3,509,214 and 3,573,206 typify the state of the art for such products.
It is well-known that many organic liquids and solids used in industrial applications, such as oils and greases, power transmission fluids, resin and polymer coatings, insulations, structural products and the like, may deteriorate when subjected to oxidation. Since these substances are very often used at high temperatures, the rate of oxidative breakdown can be very rapid. This problem is particularly important in the operation of modern day automotive and aircraft engines. The breakdown of the lubricating oil, either natural or synthetic, is frequently accompanied by the formation of corrosive acids, sludge and other breakdown products. These resulting products can harm the metal surfaces of the engine and interfere with the efficient operation of the lubricants.
U.S. Pat. Nos. 3,509,214 and 3,573,206 disclose that the stability of the organic compounds used in such lubricants which are normally susceptible to oxidative deterioration could be unexpectedly improved by the addition thereto of an N-arylnaphthylamine containing lower oligomer obtained by subjecting said N-arylnaphthylamine or mixture of said N-arylnaphthylamine with a diphenylamine or a second N-arylnaphthylamine to either thermal or chemical oxidation or both.
U.S. Pat. No. 3,336,386 describes N,N'-diisopropyl-1,5-naphthalenediamine and related dialkylated derivatives as being useful antioxidant stabilizers for elastomers.
U.S. Pat. No. 3,535,243 describes lubricant additives which are inter alia N-alkylated diaminonaphthalenes, but this reference specifically teaches away from the presence of unsaturated substituents on such molecules. U.S. Pat. No. 2,070,521 discloses various dialkylnaphthylamines as antioxidants, but there is no mention of naphthalenediamine derivatives. U.S. Pat. No. 3,406,202 describes N-alkenyl substituted naphthylamines, but there is no mention of naphthalenediamine derivatives. Additionally, the compounds of this patent must also be substituted on the aromatic ring by a --SR group which is not present in the instant compounds. U.S. Pat. No. 2,004,526 teaches N-aryl substituted naphthalenediamines as antioxidants, but these are compounds clearly outside the scope of the instant invention.
A number of N-alkyl substituted 1,8- or 1,5-naphthalenediamine compounds are known in the prior art as seen below:
J. Phys. Chem. 86, 1277 (1982) describes N,N,N',N'-tetramethyl-1,5-naphthalenediamine;
J. Org. Chem. 51, 370 (1986) describes N,N'-dimethyl-1,8-naphthalenediamine;
J. Chem. Soc., Perkin Trans. 1, 2840 describes N,N,N',N'-tetra alkylated 1,8-naphthalenediamines;
Zh. Org. Khim. 17, 1005 (1981); Chem. Abst. 95, 187185r describes the general synthetic methods used to prepare di-, tri- and tetra-N-substituted 1,8-naphthalenediamines;
Zh. Org. Khim. 20, 1567 (1984); Chem. Abst. 102, 6382x (1985) describes N-ethyl-1,8-naphthalenediamine;
Ind. Eng. Chem., Prod. Res. Dev. 23, 21 (1984) describes N-octyl-1,5-naphthalenediamine and N-octadecyl-1,8-naphthalenediamine as antioxidants for lubricants;
ACS Div. Petroleum Chem. 27, 362 describes N-octyl- and N-octadecyl-1,8-naphthalenediamine; and
Japanese Sho 60-81268 (=Chem. Abst. 103, 125225d (1985) describes N,N'-didodecyl-1,8-naphthalenediamine.
The instant invention pertains to N-alkenylated, preferably N-allylated, naphthalenediamines and N-methylene-thio substituted naphthalenediamines which have been found to have superior antioxidant properties in lubricant compositions.